Synchronizing means for audio-visual apparatus



United States Patent O This invention relates to audio-visual apparatus and more particularly for means for synchronizing a film advance motor in synchronism with electrical pulses incorporated in the audio recording.

More particularly the invention relates to audio-visual apparatus of the type having a, strip film for providing a sequence of views, an audio apparatus describing each view. The audio recording may be a conventional rec- 0rd. It is desirable to synchronize the film presentations with electrical signals placed .on the audio recording. These signals may be 30 cycle pulses which are inaudible.

The system described is intended to provide an audio program as well-as actuation pulses for synchronization of projected picture material. Both audio and pulse information are' derived from a disk record, or with a slight modification from tape. recordings. Audio material is amplified and reproduced through either loud speakers located near or within the projector frame advance mechanism.

Accordingly, a principal object of the invention is to provide new and improved audio-visual apparatus.

Another object of the invention is to provide new and improved means for; synchronizing visual presentations with audio presentation means.

Another object of the invention is to provide new and improved means for synchronizing visual presentation means with audio presentation means utilizing inaudible pulses on said audio recording, a tuned reed tuned to said pulses, said reed actuating a one revolution film advance means which is adapted to advance the film one frame.

These and other objects of the invention will be apparent from the following specification and drawings of which:

FIGURE 1 is a schematic circuit diagram of an embodiment of the invention.

FIGURE 2 is a schematic circuit diagram of a modification of the invention.

Referring to FIGURE 1, starting at the phono pickup P a pulse signal is furnished to the grid of the amplifier V1. The pulse is amplified by pentode V1 and fed through condenser C3 to the coil of a resonant reed relay D. The relay consists of a coil which surrounds a reed R sharply tuned to the pulse frequency, When the coil is provided with a signal at the resonant frequency of the reed, it causes the reed to vibrate mechanically. Signals of other than pulse frequency in the coil have little or no effect upon the reed, since the least amount of power to activate the reed is required at the resonant frequency and more and more power is necessary as the frequency decreases or increases away from the resonant center frequency.

For example, if the reed is tuned to 30 c.p.s. (the actual pulse frequency) it will activate with less than 20 milliwatts of signal in the coil. However, it will not activate with 300 mw. of signal of 50 c.p.s. Activation of the reed means vibration enough to cause contacts at- 3,259,010 Patented July 5, 1966 tached to the reed to close periodically at the vibration frequency.

Each time the contacts of reed relay D close during vibration, a momentary pulse is fed to the combination of condenser C5 and the coil K1 in parallel, through resistor R5. This causes C5 to slowly charge toward the voltage necessary to cause relay K1 to operate. At this value K1 operates closing contacts B and C and causes frame advance motor M2 to operate, advancing a frame of film.

The value of resistor R5 is selected to provide a delay in the operation of relay K1 by virtue of the time constant of R5 and C5, This prevents inadvertent pickup of K1 due to transient pulses from low notes in the audio channel or mechanical vibrations of the reed due to spurious signals or mechanical shocks to the system. Capacitor C6 provides contact protection for the reed contacts.

Audio signal is fed from the pickup to volume control potentiometer R2 through C2. Capacitor C2 blocks low frequency signals so that 30 cycle pulses are not heard in the audio output. Audio signals are fed to the grid of V2 in a manner which is conventional for an audio amplifier. The amplifier V2 is connected through transformer T1 to speaker S.

The power supply for the amplifier is typical using a silicon half wave rectifier CR1 and a simple R-C filter.

The system described above uses a 30 cycle tone mixed with the audio on the record as an advance pulse. The minimum pulse duration is A second. This allows for the use of 30-50 cycle pulse records now available in the record-strip film market, however, use is not made of the 50 cycle tone contained in the already available material. The 50 cycle tone does not have a detrimental effect upon the operation of the unit. The 3 cycle tone must be recorded at a minimum level of 18 db as given in the standard NARTB characteristic. Frequency accuracy is 30 c.p.s.i1 c.p.s. and maximum distortion is 10% harmonic distortion. Timing accuracy is 25-.|-.50% c.p.s. of one second.

There is no limitation on the pulse frequency although choice of 30 cycles places the pulse below the practical audio range and thus it can be eliminated from the audio program without affecting the audio band-width or response of the unit appreciably.

Phonograph Motor M1 is connected across the lines L1 and L2. Projector lamp L and its switch S are also connected across the lines as are the filaments F1 and F2 of the vacuum tubes.

The on-oif switch S1 is connected in the lines L2 and is part of the tone control R7. The other components are conventional.

The unit described above is primarily intended to synchronize audio programs with strip and slide film presentations. It may utilize record material, however, through the addition of suitable preamplifiers, recording tape could be used as a source of signal with equal facility.

FIGURE 2 is a variation of the above circuit which is provided. When switch S3 is in the X position the unit operates as originally described. When the switch S3 is in the Y position the unit operates in another mode utilizing the same principle.

In this mode the phono turntable operates normally through a circuit established through contacts C and A of relay K1 when the unit is turned on. When a pulse is detected, relay K1 pulls in as described disconnecting the phono motor M1 which stops. Relay K1 then holds itself in through contacts C and B. When switch S2 is momentarily closed, capacitor C5 and relay K1 coil are shorted out by dropping the voltage across them to zero causing relay K1 to open restarting the phono motor M1.

This new mode of operation can be applied to simple teaching devices. In these devices the audio program describes an operation to a student after which a pulse stops the record to allow the student to practice the operation. A dead band is placed on the record with no sound so that no objectionable sound is heard while the turntable coasts to a stop. Pushing the switch S2 restarts the record. This unit may be used with either projected film or printed material. When used with projected film material it can be arranged so that actuation of switcli S2 also advances the film one frame.

Therefore, a system is described for detecting inaudible pulses from audio record material utilizing a unique system for ferreting out inaudible synchronizing pulses. The system in effect uses a sharply tuned mechanical filter in the form of a vibrating reed. The reed in turn reconverts its vibration to electrical pulses which are integrated to ultimately actuate a relay which supplies pulses to operate or stop a motor driven mechanism.

Motor M2, the film advance motor, is a conventional motor means which is adapted to advance the film one frame each time it is actuated by a one revolution mechanism, not shown. Other equivalent one cycle motor means may be used.

Typical values for the embodiments shown are as follows:

Symbol: Value R7 megohms .5 R6 ohms 220 R4 d 33 R3 do 3,000 R2 megohms 1 R1 do 5.1 C8 mfd .47 C7 mfd .1 C5 mfd 50 C3 mfd 1.0 C2 mfd .0022 C6 mfd .0022 C1 .0068 V1, V2 60FX5 R9 ohms 12 R8 do 150 C4A-4D mfd- 4 X 50 4 The tuned reed relay D may be a conventional device. Many modifications maybe made by those who desire to practice the invention without departing from the scope thereof which is defined by the following claim.

I claim: In audio-visual presentation means, a phonograph motor, a film frame advance motor, a phonograph pickup adapted to pickup audio content and inaudible synchronizing pulses from a record, means to separate said audio content and said synchronizing pulses,

means to amplify said synchronizing pulses,

means to connect to said amplifying means to detect said synchronizing pulses comprising integrating means,

a control relay connected to said integrating means,

said relay being adapted to control said film motor,

two position switch means connected to said control relay, said film motor and said phonograph motor to stop said phonograph motor and a push button switch connected across said integrating means and adapted to start said phonograph motor, said two position switch means being connected to provide two modes of operation,

said two position switch means being connected in said first position to continuously energize said phonograph motor and connected to said relay to stop said film motor when a pulse is received,

said two position switch means being connected in said second position to energize said phonograph motor through said relay until a pulse is received and then to stop said phonograph motor until manually restarted by said push button switch.

References Cited by the Examiner UNITED STATES PATENTS 2,096,020 10/ 1937 Adair et al. 2,141,203 12/1938 Abbott 88-28 2,558,669 6/1951 Breen 88-28 X 2,787,669 4/1957 Plan et a1.

NORTON ANSHER, Primary Examiner.

WILLIAM MISIEK, Examiner. 

